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C1.4 - Crude Oil & Fuels

Crude oil, alkanes, fractinal distillation & fraction properties, combustion & pollution, environmental impact, alternative fuels

J Amuah-Fuster

on 8 July 2016

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Transcript of C1.4 - Crude Oil & Fuels

Propane + Oxygen Carbon monoxide + Water
C3H8 +
CO +
Incomplete combustion of propane
Remains of dead animals and plants that died millions of years ago.
Examples include natural gas, crude oil and coal.
Finite resource (non-renewable).
Increase the amount of carbon in the atmosphere.
C1.4 Crude oil and fuels
Crude oil is a
fossil fuel
It was formed from the decay of buried dead sea creatures millions of years ago.
We are using it up faster than it can be formed, therefore, it is
Hydrocarbons with
smaller molecules –> lower boiling points
– condense at the cool part of the tower
Long molecules - Strong forces of attraction between molecules means:
High boiling points
Low volatility (difficult to ignite)
Viscous (thick)
Separate crude oil using fractional distillation
Crude oil must be separated by
into its different substances before it can be used.
Nearly all compounds in crude oil are made from atoms of
Properties of each fraction depend on the size of the hydrocarbon molecules
Impurities in fuels may produce other substances which may be poisonous and cause pollution
Hydrocarbons in car engine
Not enough oxygen inside car cylinders, so instead of all changing to carbon dioxide, produces carbon monoxide instead.
Catalytic convertors
Exhaust gases in the catalytic converter pass over transition metals, arranged with a large surface area. Carbon monoxide and nitrogen oxide react to produce carbon dioxide and nitrogen gas. This reduces the harmfulness of the pollution
Energy can be produced from rubbish in an incinerator
Advantages - removes waste from landfills; cheap energy
Disadvantages – produces dioxins which may be harmful to health and the environment.
A Burning Problem
Lesson Objectives
Most fuels contain carbon and hydrogen, and may contain some sulphur
Burning fuels releases heat and the oxides of elements in the fuels
Understand about some of the environmental problems caused by these oxides.
Our main fuels are
natural gas
Coal is mainly
Oil and natural gas are mainly hydrocarbons (made of
carbon and hydrogen atoms only
When a fuel burns, combustion reactions oxidise the carbon and hydrogen into carbon dioxide and water (vapour):

hydrocarbon + oxygen carbon dioxide + water
How does burning fossil fuels affect the environment?
Short molecules - Weak forces of attraction between molecules means:
Low boiling points
High volatility (easily ignited)
Low viscosity (runny)
C1.13 - Crude Oil
Lesson Objectives
Describe what Crude oil is
Explain how oil companies get useful fractions from crude oil
Crude oil separated in a fractionating column
decreases going up the column
Fossil Fuels
Uses of fractions
separates liquids with different boiling points
Fractional distillation
Hydrocarbons with


higher boiling points
– condense at the hot part of the tower
Crude oil is separated into fractions using the
different boiling point of different hydrocarbons
The smaller the hydrocarbon the lower the boiling point
The uses of fractions depend on their physical properties.

Fractions that burn easily (like natural gas) can be used in cookers and central heating boilers.

Fractions with longer hydrocarbons burn less easily but provide more energy when burnt (like diesel).
The longest hydrocarbon chains (residue) are used to coat the surface of roads (tar)
Crude oil – a
of many different
These are compounds made up of
only carbon and hydrogen
Quick check
Name three fossil fuels.
Explain why oil is a finite resoure.
Describe how crude oil was formed.
As it is a mixture, the molecules in crude oil are not chemically bonded, meaning they can be separated.
Each of the different hydrocarbons has its own properties even though it is in a mixture.
Quick check
Explain the meaning of the word 'hydrocarbon'.
Explain how you could separate a mixture of:
Solid and a liquid.
Two or more liquids with different boiling points.
A grade
C grade
E grade
Give two characteristics of fossil fuels
What is a crude oil fraction?
Name three fraction of crude oil and give their uses.
Describe how crude oil is separated into fractions by fractional distillation. Use the words
in your answer
All carbon atoms have a single covalent bond with other carbon atoms; they contain as many hydrogen atoms as possible in their structure.
Hydrocarbons are molecules that contain only carbon and hydrogen atoms
Saturated hydrocarbons
Lesson Objectives
Use molecular and displayed formula to represent alkanes.
Know the formula of the first four alkanes
LPG (liquified petroleum gas)
A propane molecule consists of 3 carbon atoms covalently bonded to eight hydrogen atoms.
Its molecular formula is C3H8. It can also be represented using its displayed formula. This shows how the atoms are arranged in its molecule. Each letter represents an atom; each line represents a covalent bond (a shared pair of electrons) between two atoms.
LPG is obtained from crude oil. It is a mixture of two hydrocarbons with similar boiling points; propane and butane.
Butane molecules are made up of 4 carbon atoms joined to 10 hydrogen atoms.
The molecular formula of butane is C4H10.
What is the displayed formula?
Propane and butane are
. Alkanes are
Most other hydrocarbons in crude oil are alkanes:
Methane is the main component of natural gas; its molecular formula is CH4
Ethane is also a gas, its formula is C2H6
Hexane is part of the petrol fraction. Its formula is C6H14
Quick Check
Draw displayed formula for methane, ethane and hexane.
Give the number of carbon and hydrogen atoms in a molecule of hexane.
All alkanes have the same
general formula
, CnH2n+2
This means that the number of hydrogen atoms in an alkane is twice the number of carbon atoms plus two.
Melting and boiling points
Igniting alkanes
Size matters
Combustion of hydrocarbon fuels releases heat energy.
The uses of alkanes as fuels depend on their properties.
Their properties deend on the sizes of thier molecules.
Short chain alkanes catch fire more easily than those with bigger molecules
The size of the molecule also influences boiling points.
The smaller the molecule, the lower the boiling point.
Pentane is a

very runny liquid at room temperature. Its smaller molecules get less 'tangled' than hexadecane, because the forces of attraction are weaker.
Hexadecane (C16H34) molecules are long. They get tangled up easily and, as a result, hexadecane is difficult to pour. It does not flow easily, we say it is a
liquid at room temperature.
The reason for this property of hexadecane is that there are forces of attraction between the atoms of different molecules. The more atoms there are, the greater the forces of attraction.
Quick Check
Describe the properties of methane that make it a good fuel for cooking.
Explain why the properties of hexadecane make it a suitable vehicle fuel when mixed with other hydrocarbons.
C grade
E grade
A grade
Give the numbers of carbon and hydrogen atoms in a molecule of pentane, C5H12.
Draw a displayed formula for pentane.
Use the general formula for alkanes to work out the molecular and displayed formula of an alkane with 15 carbon atoms.
Explain why an alkane with molecular formula C18H38 is not an ideal cooking fuel.
Complete combustion of propane
Propane + Oxygen Carbon dioxide + Water
C3H8 +
CO2 +
Propane + Oxygen Carbon (soot) + Water
C3H8 +
C +
Incomplete combustion of propane
What is global warming?
Global effects
Modern life depends on energy from burning fossil fuels, but there are problems:

Fossil fuels are
there are limited resources and when they run out, they're gone.
Carbon dioxide is a
greenhouse gas
and contributes to
global warming
, one of the consequences is rising sea levels.
If combustion occurs
without enough oxygen
poisonous carbon monoxide is produced
, as well as
carbon (soot)
What is global dimming?
How is acid rain caused?
Earth's surface is warmed by the Sun, and then emits infra-red radiation back into space as it cools.
Carbon dioxide absorbs some of this energy.
Increasing levels of carbon dioxide absorb more infra-red radiation.
Less heat escapes, and Earth gets warmer.
Smoke (soot) from incomplete combustion of fuels may lead to decreased amounts of light and heat reaching Earth.
This may lead to reduced photosynthesis and the cooling down of Earth; disrupting weather patterns.
When fossil fuels like coal are burned, they often contain Sulphur, which reacts with the oxygen to produce sulphur dioxide (SO2).
Often combustion reactions can get so hot that Nitrogen and Oxygen in the air can react, producing nitrogen oxides (NOx)
The acidic gases escape into the atmosphere and dissolve in the water droplets that form rain clouds.
once dissolved, the gases become acidic solutions of
sulphuric acid
nitric acid
These 'acid rain' clouds are then carried by the wind to other locations, often thousands of miles away, before they precipitate (rain).
What happens when a fuel burns?
Propane + Oxygen Carbon (soot) + Water
C3H8 +
CO +
Incomplete combustion of propane
Sulfur dioxide
causes acid rain Most fuels contain some sulfur, which reacts with oxygen when burned
Biodiesel / Oilseed rape
Plants take in the same amount of carbon dioxide they give it out when burnt.
Overall this cancels out. We say they are
Carbon Neutral
Gasohol / Bioethanol
Plants that make sugar produce ethanol by fermenting the sugar using yeast.
Can use this by adding to petrol
Less pollution – burns more cleanly
Reduces oil needed
Incomplete combustion
Alternative Fuels
Hydrogen fuel
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